A versatile ankle-mounted fall detection device based on attitude heading systems

In this paper we propose a wireless wearable device for real-time fall detection attached to the ankle user. This device can also be embedded inside the footwear with similar performance and a lower invasiveness of use. It contains a 3-axis accelerometer, a 3-axis gyroscope and a 3-axis magnetometer realizing an Attitude Heading Reference System (AHRS). The AHRS provides the correct 3D orientation through an implemented data fusion algorithm. On sensor board is also implemented the automatic fall detection algorithm handling the orientation data from AHRS and the acceleration data from the triaxial accelerometer. The fall is a critical event that can cause physical and psychological effects particularly among older people. The elderly timely assistance after a fall could prevent serious health care consequences. For this reason the alarms generated by fall detection algorithm are sent to a smartphone via the Bluetooth module integrated into the device. In the smartphone runs a background application that sends sms alert to preset phone numbers or makes prerecorded phone calls after receiving alarms from the sensor node. In order to evaluate the performance of the proposed fall detection system, the developed device has been tested according to an experimental protocol in which volunteers perform simulated falls, simulated falls with recovery and activities of daily living (ADL). Our ankle-mounted devise shows a significant improvement in performance compared to other devices proposed in literature. In fact, the results of the experimental protocol show a sensitivity of 97% and a specificity of 100%.